Nitride Compounds: Property Anomalies Near Structural Instabilities

非技术描述：该项目正在开发一种新型材料，由两种不同材料的混合物组成。 自然地，这两种材料不会混合;然而，如果人工混合，则混合物表现出独特的性质，因为微小的外部刺激可以导致材料结构的巨大变化。这种材料的独特性能包括在施加电压或磁场时的强烈变形。例如，这种材料可用于构建新型频率滤波器，这将使移动的设备的数据速率增加十到一百倍。这些新特性可能有助于一系列变革性应用，例如，包括用于生物医学植入物的磁驱动微型开关、在没有任何外部电源或通信路径的情况下运行的核电站中的紧急阀、在频繁的温度循环下仍保持功能的坚韧和弹性涂层（用于高温燃料高效喷气发动机的可能应用）。技术专长：该项目正在发展对三元氮化物ABN中结构不稳定性的理解，其中AN和BN形成不同的平衡晶体结构。关键的想法是，具有中间组合物的这种三元化合物的单相固溶体表现出结构不稳定性，导致异常的物理性质，包括可逆的塑性变形或发散的压电响应。三元氮化物层通过反应溅射沉积。外延约束，成分变化，和离子表面相互作用被用来控制新兴的阶段，微观结构，纹理，应变，和可能的相分离。利用原位X射线衍射、拉曼和红外光谱研究了高温高压下单相固溶体三元氮化物的结构不稳定性，确定了结构-应变-能谱。新兴的异常性能的测量和理解如何结构的不稳定性导致可逆的塑性变形，各向异性的有效泊松比，在压电响应的发散，磁-机械耦合，和可逆的应力诱导剪切变换的开发。该项目包括对研究生和本科生进行最新材料合成和表征方面的培训，以及参与重大的外联工作，以鼓励女孩考虑从事科学和工程职业。

NON-TECHNICAL DESCRIPTION: This project is developing a new type of material consisting of a mixture of two different materials that are forced together. Naturally these two materials would not mix; however, if mixed artificially, the mixture exhibits unique properties because a small external stimulus can lead to a large change in the material structure. The unique properties anticipated for this material include a strong deformation when applying a voltage or a magnetic field. For example such a material is useful for building a new type of frequency filter, which would increase the data rate of mobile devices by ten to hundred times. These new properties may facilitate a whole range of transformative applications, including, for example, magnetically driven micro-switches for biomedical implants, emergency valves in nuclear power plants that operate without any external power source or communication pathway, tough and resilient coatings that remain functional despite frequent temperature cycling (for possible application in high-temperature fuel-efficient jet engines).TECHNICAL DETAILS: This project is developing an understanding of structural instabilities in ternary nitrides ABN where AN and BN form different equilibrium crystal structures. The key idea is that single-phase solid solutions of such ternaries with an intermediate composition exhibit a structural instability that leads to anomalous physical properties, including a reversible plastic deformation or a diverging piezoelectric response. Ternary nitride layers are deposited by reactive sputtering. Epitaxial constraints, composition variations, and ion-surface interactions are used to control the emerging phases, microstructure, texture, strain, and possible phase separation. The structural instabilities of single-phase solid-solution ternary nitrides at elevated temperature and pressure are studied to determine the structure-strain-energy landscape, using in situ x-ray diffraction, Raman and infrared spectroscopies. Emerging anomalous properties are measured and an understanding of how the structural instability leads to a reversible plastic deformation, an anisotropic effective Poisson's ratio, a divergence in the piezoelectric response, a magneto-mechanical coupling, and a reversible stress-induced shear transformation are developed. The project includes training of graduate and undergraduate students in state-of-the-art materials synthesis and characterization, as well as involvement in major outreach efforts to encourage girls to consider a career in science and engineering.